1. Field of the Invention
The subject invention relates to polyol compositions which are alkylene oxide adducts of vicinal toluenediamine and a co-initiator selected from the group consisting of glycerin, pentaerythritol, sucrose, sorbitol, trimethyolpropane and mixtures thereof. The subject polyol compositions are particularly useful in the preparation of rigid polyurethane foams.
2. Description of the Prior Art
It is known that alkylene oxide adducts of various initiator compounds containing two or more active hydrogen atoms, as determined by the Zerewitinoff test, are useful in the preparation of polyurethane foams. It is also known that in order to prepare rigid polyurethane foams, the alkylene oxide adducts must have low equivalent weights and high hydroxyl numbers such as 300-600. In order to prepare such adducts, initiator compounds are used which have higher functionalities, i.e., from 4-8. Moreover the amount of alkylene oxide used is less than that which would be used for preparing flexible polyurethane foams.
It is known that 2,4-toluenediamine, 2,6-toluenediamine, and mixtures thereof can be used as initiators for the preparation of alkylene oxide adducts which can be used to prepare rigid polyurethane foams. In particular, a mixture of toluenediamine isomers consisting of about 80 percent by weight of 2,4-toluenediamine and 20 percent by weight of 2,6-toluenediamine (hereinafter referred to as 80/20 toluenediamine) has been used as an initiator compound.
One of the problems, however, associated with the use of 80/20 toluenediamine is that the resulting alkylene oxide adducts have viscosities which make them difficult to handle and process. One way of reducing the viscosity of the adduct is to use ethylene oxide rather than propylene oxide. Another way of reducing the viscosity is to first react the 80/20 toluenediamine with ethylene oxide to form an intermediate adduct and react this intermediate with propylene oxide.
Although these techniques will reduce the viscosity, there is still a need to develop more effective techniques of reducing the viscosity of toluenediamine adducts in order to reduce the expense and problems associated with using such adducts.